PAUL James wrote: > Looks like u2 is a low pass filter that is AC coupled to the next stage. Yes, but it has a gain of one and isn't performing any impedence buffering either. The filter functions could be just passive parts between the two other opamp stages. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist